collect all obs modules in one folder

dartwrf/assim_synth_obs.py

dartwrf/create_obs_upfront.py

dartwrf/obs/create_obsseq_in.py

dartwrf/obs/create_obsseq_out.py

dartwrf/obs/obskind.py

dartwrf/obs/obsseq.py

dartwrf/obs/obsseq_2dim.py

dartwrf/obs/obsseq_to_netcdf.py

dartwrf/obs/run_obs_diag.py

dartwrf/workflows.py

tests/test_assim.py

tests/test_dart-rttov.py

tests/test_obsseq.py